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2. 2. What are the 3 evolutionary units of vertebrate skulls? What were these units associated with, initially? What is the germ
layer origin of each unit? Which of these units develops first as cartilage that may be replaced with bone? Which unit
ossifies directly in connective tissue?

The three evolutionary units of vertebrate skulls are: chondrocranium, splanchnocranium, and dermatocranium. Chondrocranium develops first as cartilage and then is broken down with bone being deposited in its place. The germ layer it is associated with is the neural crest and mesodermal mesenchyme. It is thought to have evolved when fragments of vertebrae perhaps became incorporated into the head as teh brain enlarged posteriorly.

Splanchnocranium first arose to support pharyngeal slits in protochordates, and is formed first as cartilage and then is replaced by bone just like chondrocranium. The germ layer it is associated with is the nerual crest or ectomesenchyme. Early on, it was thought to have provided elasticity for the pharynx and a site for muscle attachments.

Dermatocranium forms from membranous bone- dense fibrous connective tissue. Neural crest and epimere mesoderm give rise to the dermatocranium. It perhaps evolved through dermal armor sinking toward the brain that then became subdermal.

3. Describe the selective pressures that may have acted on the origin of splanchnocranium, in the transition from a chordate to
early jawless vertebrate. Describe the evidence that suggests that the dermatocranium of the skull evolved later than the
neurocranium & splanchnocranium.

The splanchnocranium is an old chordate structure that is associated with the filter-feeding surfaces seen in species such as amphioxus. It supports the gills and acts as a place for respiratory muscles to attach in vertebrates, and also contributes to jaws and the hyoid apparatus in jawed organisms. The jaws allowed for the capture of prey rather than strict filter feeding alone and allowed for a greater nutritive intake. The splanchnocranium is the most ancient component of the cranium, and the dermatocranium and chondrocranium developed later.

6

How might the 1st set of gill arches been modified to form jaws? Which element of that branchial arch formed the palatoquadrate? Which element of that branchial arch formed the Meckel’s cartilage? How was the second branchial arch modified? Diagram these elements of that second arch in a side view in relation to the jaws & neurocranium: hyomandibula, ceratohyal & basihyal (see version 3 in your notes). What are the functions of this modified 2nd branchial arch?

The formation of jaws arose out of the expansion of the first set of gill arches, namely the first epibranchial and the first ceratobranchial (see Kardong pages 239-240 and versions 1 & 3 in the lecture notes). The epibranchial element of the first branchial arch formed the palatoquadrate, while the ceratobranchial element of the first branchial arch formed Meckel’s cartilage (see versions 1 & 3 in the lecture notes). The modified second branchial arch, and more specifically the hyomandibular portion of it, serves to join the neurocranium and the jaws (see version 3 in the lecture notes).

Agnathan (jawless)- see version 1
Neurocranium: the neurocranium is largely the region of the skull that develops as cartilage. These include the olfactory/nasal capsule, the otic capsule, the optic capsule and the brain case cartilage region.
Splanchnocranium: the Splanchnocranium is the original gill or the brachial arch supports. In Agnathan, these arches are all uniform, each with three parts: the epibranchial, the ceratobranchial, and the basiobranchial.
Dermatocranium: the dermatocranium is completely absent in agnathan ( is absent in all chondrichthyes).

Jaws of a Shark- see version 2
Neurocranium: the neurocranium in jawed sharks remain very similar to that of agnathan. The area of the otic capsule is now adjacent to the enlarged first and second arches of the splanchnocranium
Splanchnocranium: The first arch retains its epibranchial (now the palatoquadrate) and cerabranchial (now Meckel’s cartilage) pieces; with the epibranchial that has become significantly widened and moved toward the opening of the mouth. The first arch now has teeth. The second arch retains all three epibranchial (now Hyomandibula), ceratobranchial (now ceratohyal), and the basiobranchial (now basiohyal). The second arch is now termed the Hyoid arch.
Dermatocranium: the dermatocranium is completely absent in all chondrichthyes.

Bony fish – see version 4
Neurocranium: It still serves as support frame underneath the brain and sensory capsules.
Splanchnocranium: The palatoquadrate becomes the quadrate and Meckel’s cartilage becomes the articular. These are replaced by bone.
Dermatocranium: the dermatocranium is largely present in bony fish. These bones now include the cranium the upper jaw, premaxilla, maxilla, palatine, pterygoid, opercular, preopercular, dentary and angular. The premaxilla, maxilla and dentary now hold all teeth.

8) Why is the origin of internal nares (choanae) an important feature of tetrapod skulls?

This feature is important because it is the first time that air can be conducted through the nares into the lungs. Before this point external nares served solely for smell, air would enter and exit externally of the mouth. Internal nares allowed for smell, but also allowed air to pass into the mouth.

Diagram to be included below.

#9 - Describe the changes in the relative proportions of the skull in front of vs. behind the eye during the evolution of tetrapods.

What bones were lost during this transition?

What evidence do we have to show that the first tetrapods were still aquatic?

What features make the recently discovered fossil called Tiktaalik such an important intermediate in this transition from Sarcopterygians to tetrapods?

Before tetrapods there was more skull behind the eye/ear region of the skull (think opercular bones). In tetrapods the jaw becomes much longer and the area behind the eye is reduced (due to a loss of bones) creating a longer 'jaw' proportion to 'behind the eye'.
The opercular bones were lost. The jaw suspension is no longer made up of the hyomandibula; it is composed of the articulate and the quadrate. The columella has been lost because it has become the stapes. The pectoral girdle is detached from the skull. The size of the splanchnocranium is reduced also.
Fossil evidence shows us that early tetrapods still had gills. This would indicate they lived in water. Some skeletons show the presence of a tail that is clearly more advantageous for locomotion in water. Also the way in which the pectoral/pelvic girdle is attached to the vertebral column suggests that the posture would have been situated to the side and used for paddling.
Tiktaalik distinctly has a neck. This is a defining characteristic of a tetrapod. This is incredible considering that the skeleton lacks limbs with digits (still used as fins.)

12. List which living tetrapods are anapsid, synapsid or diapsid. How are lizard and snake skulls modified from the typical diapsid pattern?
What is the functional benefit of these modifications within lizards & snakes? Diagram how the skulls of modern turtles are emarginated. What is the advantage of increasing the degree of emargination in a turtle skull?

The lower temporal fenestrations of lizards is not circumscribed in dermatocranium (basically, it lacks a cheekbone) so this fenestration appears as a pronounced invagination of the cranium. Snakes have lost the lower arches of both the lower and upper temporal fenestrations, so that they appear as if they lack any additional cranial fenestrations but just have a massive invagination in the lateral temporal region.
They lighten the skull and they provide greater jaw motility and flexibility with which to capture and consume prey. The snake’s extreme modifications allow the swallowing of whole, even living prey.Large emarginations provide cranial attachment points for jaw muscles that are generally made available by the temporal fenestra in diapsids and synapsids. So, functionally, they are analogous to such fenestra.

13: Discuss the two hypotheses for the origin of snakes. What are the arguments and/or evidence for each hypothesis?

The two hypotheses for the origin of snakes are the Fossorial Origin hypothesis and the Marine Origin hypothesis. The Fossorial Origin hypothesis states that snakes are most closely related to terrestrial lizards and reduced their limbs on land. They also loss their ear drums, eyelids and other sensory organs. Snakes formed a rigid braincase and are thought to be similar to Amphisbaenids, which are burrowing organisms. The alternative hypothesis is the Marine Origin which states that snakes are most closely related to Cretaceous marine lizards such as mosasaurs and reduced their limbs in water. Mosasaurs are giant monitor lizards which lived in the water and are not alive today. The similarities in bones are the symphyseal hinge (right and left dentary) and the intramandibular joint (mid point). Scientists also found early snakes in the water that had hindlimbs such as the Pachyrhachis Problematicus.

14. The human ear has three parts. List the parts, the functions, and what other groups of organisms have these parts.

The three parts to the human ear as well as there functions are:
1.Inner Ear
a. The inner ear contains the semicircular canals which allow the animal to achieve equilibrium. It is involved in balancing of the animal
b.The inner ear also contains nerves which convert the vibrations into signals which are sent to the brain to be administered as sounds.
c.Inner ear is also present in amphibians, fishes, tetrapods, and birds.
2. Middle Ear
a.The middle ear contains the tympanum, middle ear cavity, and three ear ossicles made up of splanchnocranium. These amplify the vibrations and carry them to the fenetra ovalis. The three ear ossicles are:
i.Incus (derived from quadrate)
1.Transmit sound to inner ear
ii.Malleus (derived from articular)
1.Transmit sound to inner ear
iii.Stapes (derived from columella – hyomandibula)
1.Delivers sound vibrations to the inner ear.
b. Middle ear is also present in amphibians, reptiles, birds. Snakes lack a tympanum.

3.Outer Ear
a.The outer ears main function is to protect the tympanic membrane as well as collect sound waves through the ear canal. There are also glands present that secrete what is known as ear wax to further protect the inner ear.
b.Outer ear is also present in some reptiles (i.e. crocodiles, alligators, caiman etc.) but absent in fish, and amphibians.

Besides for humans, terrestrial mammals and birds have a three part ear. Phylogenetically after the therapsids (before mammals) mark the beginning of three ear ossicles.The benefit to having three parts as opposed to one or two is that these mammals are able to detect higher frequency sounds than the other tetrapods.

15. Describe the change in the size of the synapsid fossa within the synapsid clade: from pelycosaurs to therapsids to mammals. Describe some of the functional benefits of this change.

The synapsid fossa gradually increased in size in from the pelycosaurs to the therapsids. In mammals however, the synapsid fossa enlarged greatly that it merges into the orbit. The thin zygomatic arches define the lower boundary of the synapsid fossa. Functional benefits of enlargement of the synapsid fossa are that the larger space allows for expansion and reorientation of the jaw muscles. This in return allows for a stronger and more forceful effective bite.

#16. Describe the changes in the palate and teeth within the synapsid clade: from pelycosaurs to therapsids to mammals. Describe some of the functional benefits of the development of a secondary palate and more complex teeth.

There are three groups that make up the synapsida clade. Pelycosaurs existed approximately 300 million years ago, therapsids were next to follow, and mammals existed approximately 200 million years ago, making them the most recent group.

PALATE:
Early synapsids (pelycosaurs) did not have a secondary plate. Instead, air came in the external nares and exited out other holes in the front of the skull. The first formation of the secondary palate is seen the cynodonts, the latest group of therapsids and closet to the mammals. Plates of bone from the maxilla and palatine come together on the roof of the mouth to separate the oral cavity from the nasal cavity. The Thrinaxodon is an example of a late therapsid with secondary plate formation (lecture notes from 1/24/06).

The evolution of the secondary palate served many purposes. Animals with high metabolic rates require continuous respiration and the secondary palate aids in breathing while chewing. Aquatic species are able to breathe when the mouth of full of water, which allows for more efficient hunting. Chewing improves processing and acquisition of energy to maintain endothermy. The palate aids suckling by young via pumping action of the throat, which creates a vacuum within the mouth without interfering with its nasal passage. Also, the secondary palate keeps the cranium rigid for high force compression and chewing.

TEETH:
Over time, teeth have become more complex. In therapsids, they loose all their teeth, except one point/cusp that comes up (seen in crocodile and lizard). Late therapsids (cynodonts) teeth are similar to mammals in that they are more complex. They have multiple points/cusp, usually three, which is a characteristic seen in mammals. Cynodonts have teeth behind canines that specialized into attaching to one another. There is a constant replacement of teeth, so if a new one wears out, a new one develops.

In mammals, teeth become even more complex. In the Morganucodon, a Jurassic mammal, you will see a mammalian-style of teeth replacement. They do not undergo constant replacement (seen in therapsid). Instead, they have two sets of teeth: milk teeth and adult teeth. The teeth are also doubled rooted into the jaw.

The evolution of more complex teeth in cynodonts allowed for specialized slicing (in addition to muscular cheeks) that would keep the food between its tooth rows. Permanent, double rooted teeth in the mammalian decreased the chance for tooth loss (and time to regenerate a new tooth) and, in turn, increased the efficiency of eating and obtaining energy.

17. Trace the relative sizes and placements of the dentary, angular, and articular bones from Dimetrodon (pelycosaur) to Thrinaxodon (therapsid) through Morganucodon (early mammal). What is the functional significance of these trends?

The general trend from most ancestral to most recent is a reduction in size of the articular and angular and enlargement of the dentary. In mammals, the lower jaw is just the dentary, while the angular has moved to form a small ring of bone that holds the eardrum (tympanum). The articular, part of the lower jaw hinge in Dimetrodon and Thrinaxodon, no longer serves that purpose in Morganucodon and is replaced by the mandibular condoyle of the dentary in mammals.

The enlargement of the dentary in becoming the lower jaw in its entirety and the I-beam shape it adopts improves the strength of the jaw. The absence of the articular from the lower jaw in Morganucodon means a stronger lower jaw. The relocation of the angular to form the support for the tympanum is important in the development of hearing.

18. Describe the change in position of the tympanum (eardrum) in fossil therapsids to mammals. How does the size difference between the tympanum and footplate of the stapes help amplify sound? Which vertebrates have an outer ear or “pinna”?

The positional change of the tympanum from therapsids to mammals is largely due to evolutionary changes in the lower jaw. Over time the dentary became larger while the quadrate and articular became smaller and more loosely attached to both upper and lower jaws making vibration easier. As these bones became smaller they evolved into the middle ear ossicles of mammals. During the evolution of middle ear ossicles the tympanum transitioned from close contact with the stapes to its current position in close contact with the malleus. (As described in lecture. Figure 7.55 in Kardong shows bone evolution)

The difference in surface size between the tympanic membrane and the footplate is great. This size difference amplifies mechanical energy from the eardrum to the oval window (the point at which the footplate of the stapes connects to the inner ear). To understand how this amplification occurs you can think of the ossicle system in the middle ear as a thumbtack. In this example the head of the tack represents the eardrum and the pinpoint of the tack represents the point at which the footplate of the stapes connects to the oval window. As sound waves travel through the external auditory canal the large tympanic membrane collects pressure that it applies in turn to the comparatively tiny footplate of the stapes thus driving the pressure into the oval window (this amplification and resultant energy is needed to convert the mechanical energy of the vibrating ossicles to hydraulic energy in the inner ear because sound does not travel well in fluids). (Gale virtual reference library)

The “pinna” or outer ear is found in mammals that do not lay eggs. Therefore, marsupials and placental mammals will have an outer ear. (As stated in lecture

The Cranium is composed of 3 distinct parts that come from separate Phylogenetic sources, Splanchnocranium, Neurocranium (Chondrocranium), and Dermatocranium.

The Splanchnocranium is the oldest part of the skull that first came about in prochordates to support the pharyngeal slits. The origin of the jaw comes from this that included the type of jaw attachments
2nd Arch Hyomandibula
1st Arch:
Palatoquadrate
Quadrate***In mammals this is the Incus
Articular***In mammals this is the Malleus.

******Both the Epiterygoid and Alisphenoid are homologous however the Alisphenoid is only found in mammals and the Epiterygoid is found in Teleost, Amphibians, Reptiles and Birds

The Neurocranium was next in the step of evolution that supports the brain and is formed of endochondral bones and or cartilage and sometimes composed of both.
**Endochondral bones:

Occipital bones
Sphenoid
Ethmoid
Pro-otic
Opisthotic

The Dermatocranium come into play in vertebrates that help form the outer skull and is composed of dermal bones.

Opercular
Premaxilla
Maxilla
Dentary

21. Trace the evolutionary origin of each of the 3 ear ossicles: malleus, incus & stapes. Which vertebrates have 3 ear ossicles?
Which vertebrates have just 1 ear ossicle, the stapes (columella)?

The malleus originates from Meckel’s cartilage, which becomes the articular of the lower jaw, and finally it becomes the malleus.
The incus orginates from the palatoquadrate cartilage &#8594; quadrate of the upper jaw &#8594; incus.
The stapes originates from the hyomandibular, which transformed into the columella, and then became stapes.
All of these ear ossicles are splanchnocranium derivatives.

25. Diagram these 4 main types of fish tails: heterocercal, hypocercal, diphycercal & homocercal. Include both the outline of the tail fin & the vertebral column in your illustrations. Give an example of a group of fish with each tail type. (Kardong fig.8.22, pg. 304 & fig. 3.10 & 3.11 pg. 91)

see picture

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Which groups of living vertebrates have a complete notochord as adults? Which group of living “vertebrates” lacks any vertebral elements? What elements of a vertebra are present in living lamprey & fossil sharks that are said to have “incomplete” vertebrae? (Kardong pg. 8.14 & 8.15 pg. 300-301

The groups that keep thier notochords through adulthood include the Haagfish and Lampreys, or Agnathans. Hagfish are the group of organisms that have a notochord, yet lack the vertebrate elements. The elements that are present in living lamprey and fossil sharks that are said to be "incomplete" vertebrate include small cartilage that are on top of the notochord.

26
Draw a side view of a fossil sarcopterygian (rhipidistian: Eusthenopteron) vertebra along with the nerve cord (spinal cord)
and notochord. That presacral vertebra has these elements as separate pieces: neural arch, intercentrum & pleurocentrum, so label all 3 of these in your drawing. In a transverse view, show how the notochord & nerve cord are surrounded by the neural arch & the intercentrum & pleurocentrum. In this transverse view, where would a rib attach?
(Kardong fig. 8.23 on pg. 305)

see picture

22
Q: Name the parts of the vertebrate skeleton that are “axial”, because they are along the midline of the body.Diagram a cross-section (= transverse section) of an early amniote embryo to show the following: neural tube, notochord, somite (paraxial mesoderm), intermediate mesoderm and lateral plate mesoderm & the coelomic cavity. Label these features &
then show & label the 3 divisions in 1 of those somites: sclerotome, dermatome & myotome. (Kardong, fig. 5.14 pg. 173)

A: The axial skeleton includes the notochord, vertebrae, ribs, and median fins (Lab 7).
See figure

27: How has pre-sacral vertebra changed from the design in question 26, to what you observe in early tetrapods? Diagram a side view showing the elements listed in question 26 as well as any new features. Which element (intercentrum or pleurocentrum) quickly enlarges to dominate the centrum in amniotes? What is the function of the zygapophyses? Are the pre- or post-zygapophyses anterior to each vertebra? In what directions are the pre and post-zygapophyses articulations facets oriented? (Whammy!)

1st part of question:
The pre-sacral vertebra have changed in 3 ways to increase strength for life on land:
1. Two cervical vertebrae (atlas and axis) came about to allow for cranial movement...fishies don't move their heads independent of their body-axis like tetrapods do.
2. Ossified centra could support a greater weight load.
3. Enlargement of one centra (pleurocentrum) at the expense of other==>less centra per segment==>reduces flexibility, but firms axial column.

2nd part of question:
You can find diagrams of what the fishies' vertebra on page 305 of your text book Fig. 8.23 (c)...and you can compare this diagram to Fig 8.27 (d) (e) on page 309 in addition to Figs 5.9, 5.11, and 5.13 in your lab manual that came with the textbook to see what tetrapod vertebra look like....major new derived trait for tetrapods=zygapophyses.

3rd part of question:
Pleurocentrum enlarges in amniotes.

4th part of question:
Function of zygapophyses=(adaptation for land tetrapods) to interlock gliding articulations (movement); they are oriented to allow bending in a horizontal or vertical plane, but they resist twisting of the axial column.

5th part of question:
For an individual vertebra, the pre-zygapophyse is anterior ("in front of" the neural arch), however, when you interlock them together, the post-zygapophyse can appear to be anterior because it sits on top of the pre-zygapophys.

REMEMBER: Anatomy party at Dante's for the inaugural Bones N'Beer at 8pm on Thursday in celebration for getting through our first lab practical. Pitchers at 8pm are only $1!! Dante's is located at 5300 Roosevelt Way NE, next to Giggles Comedy Club.

12. Draw side views of the dermatocranium of the cranium (no lower jaw) to show anapsid, synapsid & diapsid skull designs.

28. Show where bicipital (two-headed) ribs may attach in both anterior and lateral views of amniote vertebrae. Label the diapophysis and parapophysis on the vertebrae and label the 2 heads of the rib: tuberculum and capitulum (Kardong fig. 8.7 pg. 294)

Primitive ribs are bicipital. They have 2 heads, capitulum and tuberculum. Each articulates respectively with the parapophysis on the intercentrum or the diapophysis on the neural arch. See pic

29
Here is the question:
Diagram each of the following centrum shapes in sagittal section: acoelous (amphiplatan), procoelous, opisthocoelous, & amphicoelous. Give an example of a vertebrate that has each type.

see diagram

36 Draw a lateral view of a left pectoral girdle & fin in a generalized shark (Chondrichthyes). Label all of these elements:
scapulocoracoid, the basal pterygiophores (pro-, meso- & metapterygium), radial pterygiophores & ceratotrichia. Draw
arrows to show the pre-axial & post-axial directions. Describe 3 major differences between this design & the pattern in a
bony fish such as Amia (Bowfin).

Attached is the drawing of the shark pectoral girdle.

Three differences between the shark and a bony fish:
-all these structures are cartilaginous in a shark and ossified in the bowfin
-instead of ceratotrichia of the shark, bony fish have dermally derived lepidotrichia
-in bony fish, the mesopterigiophore splits into smaller bones, rather than just the single large one in sharks.

35. Place these traits by their first appearance, on a cladogram that includes these groups: hagfish, lamprey, other fossil
jawless fishes, Placodermi, Chondrichthyes, Actinopterygii & Sarcopterygii: caudal fin, pectoral fins, pelvic fins, limbs with
digits.

Using a cladogram that places Hagfish on the left and progresses to the right just as it is listed above; the development of the caudal fin would be between Lamprey and (other fossil jawless fish), the development of pectoral and pelvic fins would both be between (other fossil jawless fish) and Placodermi, and the development of limbs with digits would be after Sarcopterygii.

Trace these general changes in these pectoral girdle bones from fossil sarcopteyygians, basal amniotes, cynodonts to
therian mammals (marsupials & placentals) using Kardong fig. 9.18 & 9.19 on pg 334-335 and fig. 9.28 on pg. 342:
a. When is the pectoral girdle free of attachment to the skull? Once free of the skull, how does the pectoral girdle
associate with the rest of the skeleton?
b. Relative size change & then loss of cleithrum & interclavicle.

a. The pectoral girdle became free of attachment to the skull in tetrapods (early amphibians as they made a transition to life on land). Once free of the skull, the pectoral girdle became indirectly associated with the axial skeleton via muscles. The rhomboideus (an axial muscle) attaches the scapula blades to the neural spine, and the seratus muscles attach the scapula to the ribs.

b. The overall trend in pectoral girdle evolution is the paedomorphism of dermal elements and the paramorphism of endochodral elements. The cleithrum is most prominent in fossil sarcopterygians and is lost in basal amniotes, cynodonts and therian mammals. The interclavicle is not present in fossil sarcopterygians, but is seen in basal amniotes and cynodonts, and is again lost in therian mammals.

34. Describe the functional benefits of paired and median fins with regard to controlling or stabilizing these types of movements: roll, pitch, and yaw. Draw arrows to show the direction of movement produced by roll, pitch, and yaw for a fish.

see document

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Q: Draw a lateral view of a left pectoral girdle & limb of a basic tetrapod (non-mammalian). Label all of these elements: cleithrum, clavicle, interclavicle, scapula, coracoid, humerus, radius, ulna, carpals, metacarpals & phalanges. Draw arrows to show the pre-axial & post-axial directions. Draw in & label the location of the glenoid fossa (where the humerus articulates with the pectoral girdle). Describe or draw from a dorsal view, how tetrapod limbs were reoriented for terrestrial locomotion.

A: In basic tetrapods, the major difference we see from earlier organisms is that the dermal content in the pectoral girdle (cleithrum, clavicle, interclavicle, etc) decreases significantly while the endochondral elements (scapula, coracoid, etc.) become the main components. In Eusthenopteron, we still saw large dermal components and small endochondral components.

In the diagram attached, the limb attaches to the Glenoid fossa depression. The forlimb pattern remains somewhat similar to earlier ancestors, yet there are some major distinctions. Modern tetrapods have a single basal pterygium (humerus), two radials (radius and ulna), many divided/branching carpals that give rise to digits, and the manus, consisting of metacarpals and phalanges. Modern tetrapods do NOT have lepidotrichia. (The number of joints in the phalanges for the tetrapod drawn from thumb to pinky is 2,3,4,5,4).

Modern tetrapods also reoriented their limbs from "pointing-out" sprawled posture to drawn underneath their bodies. Figure 9.31 and 9.32 on pg. 345 in Kardong nicely illustrate this change. This rearrangement allows for more efficient terrestrial locomotion. The radius has changed with respect to the orientation of the body, as it is now cross the ulna. Thus, it is best to remember that the radius is on the "thumb" side.

32
Define appendicular skeleton
What are the general functions of the pectoral and pelvic girdles?
Describe the germ layer origins of the appendicular skeleton:

The appendicular skeleton consists of the paired fins or limbs, the pectoral or shoulder girdle, and the pelvic or hip girdle. (Kardong p. 321)The pectoral girdle supports the pectoral fins or limbs and has both dermal and endochondral skeletal elements. In fish, it connects directly to the back of the skull. In tetrapods, the pectoral girdle is no longer connected, and the dorsal series of dermal bones is lost. (Kardong, p. 330) The pelvic girdle supports the pelvic fins or limbs, and consists only of endochondral skeletal elements. In most fishes and some early tetrapods, the pelvic girdle consists of just one element. But in modern tetrapods, there are three: the ilium, ischium and pubis. Via the ilium, the pelvic girdle attaches to the vertebral column and defines the sacral region. (Kardong, p. 333)The appendicular skeleton is derived from the paraxial mesoderm (somites), specifically the myotomes. (Kardong p.175, http://courses.washington.edu/chordate/453lectures/germ-layer-derivatives.pdf)

41
Q: Compare the changes in the shape & relative sizes of ilium, ischium, & pubic bones in the pelvic girdles of early amniotes to therapsids and then mammals. What unique bone is part of the pelvic girdle of marsupials?

The ilium, ischium, and pubis are all about the same size in early amniotes and each bone is triangular in shape. The ilium bone has a small posterior projection on it. In Therapsids the ilium is much larger in size and now has a anterior projection on it as well causing it to look like a hammer. The ischium and pubis are a little bit smaller in size than they were in the early amniotes and there is a hole that goes across the midline where the ischium and pubis bones meet. Mammals pelvic girdle looks significantly different when compared to early amniotes. Mammals have an ilium bone that is about the same size compared to early amniotes but it is swept forward and is very long. The ilium is larger than both the ischium and pubis, however the pubis has reduced in size in the mammals and now is considerably smaller than both the ischium and ilium. Mammals also have a hole at the point where the ischium and pubic bones meet. (refer to Kardong fig.9.21)

- Marsupials have a prepubis bone in their pelvic girdle that may be related to the fact that they have pouches.

The fin-fold theory suggests that primitive paired fins originated from paired but continuous ventrolateral folds in the body wall that were supported by a transverse series of endoskeletal pterygiophores, the basals and the radials. The basals and the radials then extended to support the fins. Divisions occurred afterward between the anterior (pectoral) and posterior (pelvic) pairs. Dermal bone was added later on to the pectoral girdle for further strengthening of the paired fins. Several indirect evidences support this theory, mainly from fossils of early fish that carried presumed remnants of fin-folds. The Myllokunmingia and Haikouichthys were examples of Agnathans that had fin-folds. The Acanthodians possessed a paired row of spines to mark where a paired fin-fold could have been in their ancestors. In addition, shark embryology have shown that a discrete paired fins developed from a continuous thickening along the lateral body wall of the shark, hinting to the ventrolateral folds. An alternative to the fin-fold theory is the gill-arch hypothesis, which suggests that the endoskeletal girdle elements came from a posterior gill arch and the development of fins arose from enlongated gill ray. Currently, the fin-fold theory is viewed as the most plausible out of the two theories.I found my answer on page 323-325 in the Kardong book. The book does not mention any evidence agaisnt the fin-fold theory, but it does present a competing, alternative theory, the gill-arch theory.

37. Draw a lateral view of a left pectoral girdle & fin of Eusthenopteron (a fossil sarcopterygian). Label all of these elements: cleithrum, clavicle, scapulocoracoid, metapterygium, radials (carefully show the branching pattern in the radial elements) & lepidotrichia. Draw arrows to show the pre-axial & post-axial directions. Explain how a tetrapod limb can readily derived from this design. Why are the earliest tetrapod fossils described as being polydactyl? See Kardong fig. 9.14 & 9.15 on pg. 331 & fig. 9.23 on pg. 339.

The first tetrapod showed changes in the appendicular skeleton correlated with locomotion on land and exploitation of the terrestrial environment. The pectoral girdle tends to lose its attachment to the skull, which allows increased cranial mobility and perhaps reduced jarring of the head, and it became stronger, more robust, and more completely ossified. Since the pectoral girdle is no longer connected to the back of the skull, the connecting skull bone (posttemporal, adjoining shoulder bones, supracleithrum, postcleithrum) are absent, leaving a dermal shoulder girdle composed of the remaining ventral elements: paired cleithrum and clavicle, and an unpaired midventral interclavicle in early tetrapods. In addition, the fins of fish ancestors were replaced by digits.

Polydactyly refers to a condition having more than five digits The earliest tetrapod fossils are described as being polydactyl because hindlimb of Ichthyostega had seven digits, the manus of Acanthostega included eight digits, and the fore-and hindlimbs of Tulerpeton had six digits. These late Devonian fossils are the earliest tetrapod remains available. They indicate that the primitive tetrapod pattern was polydactylous and the five-digit pattern is a later stablization.

39 c,d,e
c. Relative size of coracoid bones (anterior & posterior).
d. In which group(s) does the posterior coracoid become a process on scapula?
e. In which group(s) is there an acromion process & spine on the scapula?

n more primitive species such as the early osteichthyes, the coroacoid and the scapula are a single element. which is called the scapulocoracoid. Then in early tetrapods, the bones become ossified from different embryonic centers which become distinct bones each called the scapula and the coracoid. Anterior coracoids of synapids are homologous to coracoids of fishes and amphibians. The Anterior coracoid is often called the procoracoid. The amphibians and modern reptiles and birds have just the procoracoid. A new center of ossification of synapsids is the posterior coracoid, often called just coracoid. The anterior coracoid and the posterior coracoid is present in primitive amniortes and monotremes. Then marsupials and placental mammals only have the posterior coracoid. The posterior coraocid becomes a process on the scapula in marsupials and placental mammals.

The acromion process and spine on the scapula is only present in marsupials and placental mammals.

40. Diagram & label the bony elements that comprise the pelvic girdle of Eusthenopteron (a fossil sarcopterygian) & the pelvic
girdle of the fossil tetrapod Ichthyostega. In the tetrapod drawing, show & label the acetabulum (socket for the femur).
What new connection is made in the tetrapod pelvic girdle? To which bone of the pelvis is this attachment made? Use
Kardong fig. 9.14 pg. 331, fig. 9.21 pg. 337 & fig. 9.28 on pg. 342.

I have attached the diagrams to this post (I apologize for my lack of artistic skills). As for the second half of the question, the new connection that is made in tetrapods is between the pelvic girdle and the vertebral column. The connection to the vertebral column is achieved thanks to the sacrum being connected to the illium bone of the pelvis.

42 Describe the similarities in the organization of the front & hind limb bones of tetrapods. Compare the arrangement and
numbers of elements using Kardong fig. 9.22 on pg. 338.

The forelimbs and hindlimbs of tetrapods are incredibly similar in their consruction. Like many other species, the forelimbs and hindlimbs of tetrapods are arranged (from proximal to distal) as carpals/tarsals, metacarpals/metatarsals, phalanges.
Beginning with the forelimb, it is arranged with two larger bones in the most proximal position, these are the radius and ulna. The radius and ulna lead into the carpals which are arranged rather sporadically in the middle of the manus. The most distal carpals lead into the metacarpals which would be known as the most proximal region of the forelimb digits. There are only 5 metacarpals, one in each digit which leads to the phalanges. The phalanges, arranged in positions I through V reading right to left looking at the manus in the anatomical position (from above, palm down, Kardong page 338). The bones of the phalanges of tetrapods are (position – number of bones) I–2, II–3, III–4, IV–4, V–3.
The hindlimb of tetrapods are arranged very much like the forelimb. Beginning most proximally, the tibia and fibula, which would be congruent to the radius and ulna, connect to the tarpals of the hindlimb, which connect to the metatarpals, again of which are 5, which connect to the chains of phalanges, again reading from right to left numbered I through V. I–2, II–2, III–2, IV–2, V–2.
Tetrapods are very similar in arrangement of elements, but vary widely in size, shape, and number. All forelimbs and hindlimbs are arranged as previously stated (radius, ulna / tibia, fibula , metacarpals/metatarsals, phalanges) but some tetrapods only have 2 digits such as horses, and some have 8 digits like acanthostega. Others may have more or fewer bones within their digits, some may have more or fewer carpals/tarsals arranged in more or fewer rows of bones, but the general construction of the manus and pes is dramatically similar.

54
Question:
If muscle length & diameter are constant, describe how proximal vs. distal insertion points (relative to a joint or pivot
point) will affect the speed of the limb’s movement & the force generated at the end of the limb. See Kardong’s fig.
10.14 on pg. 379.

A muscle that is constant at both length and diameter will move a limb the same distance whether proximal or distal. However, If the insertion point of the muscle is proximal to the joint, the arm may move faster with longer sweeps of the end of the limb than if it was a distal insertion. Distally, the muscle moves the limb less in a given time, but as a trade off, expresses more strength due to more leverage (i.e., swing a door open pulling farthest from the hinges pg. 278-9).
As the muscle's insertion point moves farther from the joint, speed reduces and force increases at the end of a limb.

43. Be able to fill in the following table & then explain the function of striations and intercalated discs:
Read Kardong on pg. 366-368

(Chart: smooth vs skeletal vs cardiac muscle)

lease see attached chart for muscle comparisons.

Intercalated Disks:
*Branched cardiac muscles are joined by intercalated disks. Waves of contraction send electrical impulses through the heart, which are spread through the cells via these intercalated disks. They fold together and “lock in”, creating a finger-like locking pattern, thus increasing the surface area for transduction. They are low resistance double membranes that represent the end of one muscle fiber, and the beginning of another.

Striations:
*Cardiac and skeletal muscle have an internal structure of highly organized myofilaments. The overlapping actin and myosin form sarcomeres, which are the functional unit of striated muscle. Actin and myosin meet like two sets of combed teeth, and are pulled together along their length when contracted. Smooth muscle has actin and myosin, but they do not have sarcomeres and are not as organized as cardiac and skeletal muscle.

52. Explain why longer muscles move the body or a fin/limb farther in the same amount of time. Why do all of the
sarcomeres of an activated cell, shorten to their minimum length, if that cell is excited? What muscle shape (see
question 50) provides the largest degree of movement per unit time, if other variables are constant? See Kardong’s
fig. 10.13 on pg. 379.

Longer muscles move farther in the same amount of time as shorter muscles because longer muscles contain more sarcomeres. The total distance sarcomeres shorten is additive, so longer muscles move farther than short muscles in the same amount of time. For example, there is one muscle that is one inch long and another that is a twelve inches long. The time it takes for both of these muscles to contract to half of their original length is equal, but the twelve inch muscle will move a distance of six inches while the one inch muscle will only move a distance of half an inch.
Sarcomeres shorten to their minimum length when activated, instead of somewhere in between, because they work on an all or none principle. Either the sarcomeres contract all the way (receive a nerve impulse) or they do not contract at all (do not receive a nerve impulse).
The muscle shape that provides the largest degree of movement per unit time is the strap muscle, because the strap muscle is a type of muscle that covers the longest distance in the body. So when a strap muscle contracts it covers a greater distance in the same amount of time as the other types of muscles.

45:
Place these structures of a muscle (organ) in correct hierarchical order from largest to smallest units or subdivisions:
sarcomere, thick & thin filaments, muscle fiber (cell), motor unit or fasicle, myofibril. Draw & label 2 sarcomeres,
showing all the parts and their relationships in relaxed vs contracted conditions. See Kardong’s fig. 10.02 on pg. 367.

From largest to smallest: Motor unit/fascicle, muscle fiber/cell, myofibril, sarcomere, thick and thin filaments. Each long myofibril is sectioned into shorter sarcomeres. On each sarcomere, thin filaments are located on either end of the sarcomere, and thick filaments are located in the center of the sarcomere. During contraction, the mobile thin filaments slide over the stationary thick filaments toward the center of the sarcomere. This shortens the sarcomere.

53
Q: Why is a muscle with a larger cross-sectional area stronger but a muscle that is longer does not gain a strength advantage?

Q: What muscle shape provides the greatest strength when all other variables are constant?

Muscles with larger cross-sectional areas have more fibers contributing to the direction of force, where a longer muscle only changes the distance the force travels but not its overall power. This is the same as trying to pull a 5 inch length piece of rope apart versus pulling a 10 inch length piece apart; they both require the same amount of force to break. The area of the cross section becomes the determinant of the breaking point and not the length because force is transferred through the length to the origin and insertion.
However with a 2” circumference rope versus a 4” circumference you will find a great difference in pulling apart the 2 versus the 4 inch piece apart and this is because the 4 inch piece has more fibers pulling against my force. Simply put the length of the fibers does not increase strength but the number present will. When all factors are made equal including cross sectional area the muscle shape that provides the most force is pinnate.

54
Question:
If muscle length & diameter are constant, describe how proximal vs. distal insertion points (relative to a joint or pivot
point) will affect the speed of the limb’s movement & the force generated at the end of the limb. See Kardong’s fig.
10.14 on pg. 379.

Response:
A muscle that is constant at both length and diameter will move a limb the same distance whether proximal or distal. However, If the insertion point of the muscle is proximal to the joint, the arm may move faster with longer sweeps of the end of the limb than if it was a distal insertion. Distally, the muscle moves the limb less in a given time, but as a trade off, expresses more strength due to more leverage (i.e., swing a door open pulling farthest from the hinges pg. 278-9).
As the muscle's insertion point moves farther from the joint, speed reduces and force increases at the end of a limb.

48. Graph and then explain the following relationship: length of an entire muscle organ on the horizontal (X) axis & passive force (tension) generated on the Y-axis, as the muscle is stretched. Since the muscle isn¡¯t contracting, describe how tension is generated during passive stretching. See Kardong¡¯s fig. 10.09 on pg. 374.

Passive tension represents the force required to stretch a relaxed muscle to greater length and results from the elastic constituents of the muscle, mainly from its collagenous fibers. Passive force increases with muscle length and it only becomes appreciable at lengths greater than the normal range. It is generated from mechanical energy resulting from gravity or motion of body parts that load the muscle like a spring, storing energy until it is released.

58
58. Draw a side view of a fish body to show the design & location of epaxial & hypaxial muscles. Include & label the
following in that drawing: horizontal septum, myomere & myosepta.

see file

Question #47Graph and then explain the following relationship: muscle fiber (cell) length on the horizontal (X) axis & force (tension)
generated on the Y-axis, as a percent of the fiber’s maximum possible force, on the vertical (Y) axis. Based on this
graph, what is the optimal resting (non-contracted) length of a skeletal muscle fiber? See Kardong’s fig. 10.06 on pg.
371.

The optimal resting length of a skeletal muscle fiber occurs at intermediate lengths. This is because the maximum number of cross-bridges are formed at this value to achieve the maximum force.

This attached graph shows the total force generated by active and passive tension.
The active tension comes from the force generated by the muscle fiber. The reason for it's bell shaped curve is due to the structure of the sarcomere. When the fiber is fully shorted it can no generate much force due to the actin and myosin overlapping each other. When the muscle is stretched out it will also not be able to generate a great amount of force because the actin and myosin are far apart. Less cross bridges are formed. The optimum position for force generation is the intermediate position when the thick and thin filaments are lined up to form the maximum amount of cross bridges. This is when the muscle is in the relaxed position.
The passive tension illustrates the tension in the muscle from the elastic collagen fibers. It is best described by the rubber band comparison. The more you stretch the rubber band the more force you can get from it. This is why this curve looks exponential.
If you add these components it will illustrate the total force a muscle can produce

63
Draw a transverse section through the trunk (thoracic region)of a tetrapod to show the location of epaxial and hypaxial muscles. Include and label in your drawing: a vertebrae with: a neural arch, transverse processes, centrum and location of spinal chord; a rib; and the epaxial and hypaxial muscles.Describe at least two changes in this design from that of a fish. See Kardong's figure 10.26 on p.388.
Describe at least two changes in this design from that of a fish.

See attachments for drawings
Fish have mostly regions of undifferentiated epaxial and hypaxial muscle masses. This axial musculature of fishes supplpies the major propulsive forces for
locomontion as well as most of the body's musculature. Secondly, a contraction spreading within the axial musculature alternates from side to side developing waves of undulation. These powerful bends are responsible for developing the boy's
lateral thrusts against the water and driving the fish forward. The tail is the most importnat part of the body generating force due to the large normal force being greater in the tail than in the trunk.

On the other hand in tetrapods the appendicular muscles are more responsible for locomotion and account for most of the muscle bulk. While the axial muscles are reduced, that which does remains differentiates into specialized muscles.
This reflects the more complicated control exerted over flexion of the vertebral column and movement of the rib cage. In salamanders the epaxial muscles are essentially one muscle mass, the dorsalis trunci. The axial muscles in salamanders reflects the continued central role of the axial cloumn in
locomotion and the hypaxial have differentiated into a few muscles. In reptiles (ie, lizards) the axial muscles split into many layers. Muscles of the epaxial region attach to vertebrae and in other species further split into additional muscle groups. The hypaxial musculature attaches to the rib cage and aids in breathing and moving the trunk.

Draw 2 simple views from the front looking at the placement of the limb bones relative to the pelvis, in 1 view show the
sprawling posture of a salamander or lizard and in the other the parasagittal posture of a bird, dinosaur or mammal.
Label the hip, knee & ankle joints.

View attachment

31. Describe or diagram how the original components of a therapsid atlas & axis vertebrae (eg. pleurocentrum, intercentrumneural arch), combine to contribute to the redesigned mammalian atlas-axis complex. (See the illustration on EPOST)

The Atlas and Axis in the therapsid are one whole piece. In the Modern Mammal the whole piece is broken down and reduced to the complex of the atlas (first vetebrae) and Axis (Second vetebrae). The Atlas is composed of the "Atlas Neural Arch, Atlas Intercentrum. While the Axis is composed of the "Atlas Pleurocentrum, Axis intercentrum, Axis Pleurocentrum, and the Axis Neurl Arch" This can clearly be seen in the figure on the epost.

The reasons for the redesign in mammals is explained in our text on page 309 where it states that "the two cervical vertebrae developed to answer the problem of maintaining bony strength while retaining cranial mobility. Atlas gives vertical (nodding) movement, while the Axis gives horizontal (tilting) movement. The two pieces divide the labor between two joints whie maintaining bony strength in the neck"

84. Describe how these traits of a bird's skeleton are advantageous for powered flight:

e. Semilunate carpal: this is part of a specialized wrist joint and has a curved upper surface. The semilunate carpal allows for increased movement, specifically flexion and extention of the wrist during flight.

f. uncinate processes on ribs: these brace the ribs to each other and stiffen the trunk during flight so the trunk does not compress against the force of the flight muscles.

g. pygostyle: this is similar to the coccyx in humans, is made of fused caudal vertebrae, and provides attachment for tail feathers which aid in steering during flight.

h. alula: this is a modified digit 2 and decreases turbulence at low speeds for more precise flight.

77. Describe 4 specialized features of the skeletal-muscle systems of the limbs/girdles that adapt large ungulates, such as horses or deer, for cursoriality (ie. features that increase stride length or increase efficiency of locomotion). Name one cursorial adaptation for humans.

85. Describe the experiment that demonstrated that chicks, before they can fly, use their wings to help them run up steep inclines. Explain how this lends support to the ground up hypothesis of the evolution of flight in birds.

Experimenters set up an incline at an extremely steep angle. They then placed the bird on the incline and recorded the bird as it climbed up the incline. As the chick attempted to climb up the incline, it successfully flapped its wings in order to accomplish the task. By flapping its wings, the chick was able to press itself into the incline and in effect prevent the bird from falling away from the incline. Flapping its wings also helped the chick to persist in keeping traction and use the traction to force itself up the slope. This behavior observed in chicks has been termed wing-assisted inclined running (WAIR) and may be helpful in supporting the ground up hypothesis concerning flight evolution in birds. This hypothesis presents the idea that the early appearance of feathers was instrumental in locomotion on land and eventually led to actual flying birds. In the evolution of flight, these early feathered forelimbs could possibly be providing advantages similar to that of WAIR or simply be representing an intermediate stage of flight origin. This dorsoventral forelimb stroke which allowed for WAIR may also be instrumental in allowing for the transition into the dorsoventral flight of later evolved birds. (Kardong p. 360)

69) On a side view of the head of a developing vertebrate, shown below, diagram & label the following: orbital and otic capsules, 7 somitomeres & 4 otic somites that will form the branchiomeric and hypobranchial musles. What is the difference between a somite & a somitomere? List the somitomeres/somites that contribute to each of these: branchiomeric muscles of brancial arch 1, 2, 3; hypobranchial muscles and extrinsic muscles of the eye.

the diagram and label, it should look like the picture of the head from Lecture 13. The orbital capsule you must draw in, which is in front of (towards the nose) of the otic capsule. In front of the otic capsule are the 7 somitomeres; behind it are the 4 somites. The branchiomeric muscles are those related to the pharygeal arches. (I'll try to get a picture up as soon as possible.)

The difference between a somitomere and a somite:
Somitomere-- these are loose masses of paraxial mesoderm derived cells that form along the sides of the neural tube. The first seven give rise to the straited muscles of the face, jaws and throat.
Somites--The remaining somitomeres bud off to forming the somites (they express several different proteins) giving rise to the three layers: sclerotome (vertebral column), myotome (associated muslces), and dermatome (dermis). The first four are involved with the mypobrancial muscles of the throat.

Somitomeres 1, 2, 3, and 5 give rise to the EXTRINSIC EYE MUSCLES.
Somitomere 4 is associated with the first arch including these muscles: the LEVATOR PALATOQUADRATE and ADDUCTOR MANDIBULI (and the SPIRACULARIS).
Somitomere 6 gives rise to the muscles of the 2nd arch: the LEVATOR HYOMANDIBULI.
The 3rd arch is asociated with somitomere 7, and the last remaining arches with the four somitomites. These areches combined give rise to the DORSAL PHRAYNGEAL CONSTRICTORS and the CUCULLARIS.
HYPOBRANCHIAL MUSCLES:
The four somites behind the otic capsule also give rise to these muscles:
1st arch to the pectoral girdle: CORACOID MANDIBULARIS
2nd arch to the pectoral girlde: CORACOHYOIDUS
3rd+ arch to the pectoral girdle: CORACOBRANCHIALIS

80. Briefly compare the key skeletal elements that form the wings of bats vs. pterosaurs.

The pterosaur has a complete radius and ulna where as the bat has a fused rudimentary ulna. The Pterosaur has 4 fingers and the bat has 5 fingers. 4th finger of the pterosaur is prominently longer than the other fingers whereas the bat has 3 longer fingers and 2 short fingers. The pterosaur has it finger along of the edge to stretch the wing, but the bat has it fingers spread throughout to stretch the wing. Pterosaur wing is more slender while bat wing is broader but shorter. The similarities between pterosaur and bat are that they both have skin membrane wing rather than feather wing of bird. They both have elongated radius, ulna, and fingers to support the wing for flying. They have hollow bone for lightweight and pectoral girdle adapted for broad wing movement.